Continuous System and Process for Treating a Low-Water Biomass Stream with Liquefied-Gas Solvent to Separate and Recover Organic Products

ABSTRACT

A method and system for the treatment of a biomass stream to separate organic extracts/biomolecules (such as proteins, lipids and/or carotenoids) from the biomass stream, wherein the water content of the biomass stream is decreased by bringing the biomass stream into contact with a compressed liquefied gas solvent, to create a low-water content biomass stream and introducing the low-water content biomass stream to an extraction apparatus that recovers one or more organic products with little or no measurable solvent residue.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of currently pending U.S.Utility application Ser. No. 13/804,446, filed Mar. 14, 2013, which ishereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a method for dewatering and separating animalprocess wastewater, vegetable and fruit waste and other industrial andmunicipal waste and post-waste streams using a liquefied gas solvent ina rotary pressure filter to yield one or more proteins, lipids and/orother useful biomass extracts.

Description of the Related Technology

Various types of separation and extraction processes are employed torecover materials dissolved or suspended in waste streams. Manyseparation methods, solvents, gases and apparatus exist to separatedifferent types and volumes of biomass into useful by-products with awide range of values, from commodities to value added ingredients. Inthe animal processing waste product industry, dissolved air flotationand other flocculation processes with or without some combination withcentrifuge processes are used most often to separate saleableby-products, such as lipids, from the animal processing wastewaterstreams. However, much of the value in lipids and proteins remain in thepost-flocculated material commonly known as “DAF” (“DAF” is an acronymfor “dissolved air flotation” and sometimes also is used in reference tothe resulting material after dissolved air flotation processing). Whilepoultry, beef, pork, dairy and fish waste streams respond differently toflocculation and centrifuge processes, significant quantities ofvaluable by-products still remain in the waste stream. By contrast,fruit, vegetable and other botanical matter may employ differentprocesses for recovering saleable by-products which apply extensive heatand pressure to produce certain extracts, although the heat and pressurecan damage the resultant products in ways that limit usefulness andtherefore their value.

Others have described methods and systems to process “DAF” and otherwaste materials. For example, U.S. Pat. No. 7,186,796 provides a methodof isolating a bio-molecule including peptides, proteins,polynucleotides and polysaccharides from a water-borne mixture bycontacting the water-borne mixture with dimethyl ether to precipitatesolid particles of the bio-molecule. The water-borne mixtures includeaqueous solutions, suspensions, emulsions, micro-emulsions and liposomessuspended in aqueous media. Similarly, U.S. Pat. No. 7,897,050 providesa method and system for the extraction of an organic chemicalconstituent, including hydrocarbons, crude petroleum products, refinedpetroleum products, synthetic compounds from a solid matter, includingfrom animal renderings, using an inclined auger in a pressurizedchamber. Thus, prior art systems have focused on higher value inputstreams, and generally worked with smaller volumes of waste materialswhere the methods, apparatus and chemistry can yield a higher valueoutput. Prior art has been limited by the cost to scale the process inthe form of cost prohibitive capital equipment needed to process largevolumes of waste streams and/or the operating cost in the form of energyrequired to separate the waste streams into valuable commodity products.

In principle, continuously and discontinuously operating pressingapparatuses, e.g. multi-platen presses, strainer presses, plate filterpresses, travelling screen presses and screw presses, are suitable forseparating off the lipids and proteins from the biomass. Centrifuges arelikewise suitable for separating off lipids from the biomass. Knowntypes of centrifuges include, for example, turnout centrifuges, peelercentrifuges, pusher centrifuges, mesh screw centrifuges, vibratingcentrifuges and sliding centrifuges and decanters. See, e.g., WO2010/001492 A1, relating generally to recovering tallow and moreparticularly, to removing fats, oil and grease and recovering tallowfrom food or animal processing wastewater by adding a flocculant andseparating the tallow from the solids employing a centrifuge.

A further method which has attained importance for separating lipids andproteins from a biomass is filtration. A distinction is made betweendiscontinuous and continuous filtering systems. Discontinuouslyoperating filters include, for example, fixed-bed filters, suctionfilters, candle filters, leaf filters and plate filters. The separationof lipids and protein from the biomass by means of discontinuouslyoperating filters is generally less preferred. A disadvantage here isthe loading and unloading of the filter, which requires a considerabletime, as well as filter clogging related to lipid viscosity exacerbatedby lower processing temperatures where liquefied gases are employed. Itis a further disadvantage that DAF, in aqueous solution, yields fluxrates that make traditional commercial filters unusable. Thus,discontinuously operating filters are not suitable for large biomassthroughputs. Large biomass throughputs can be categorized as severaltons of input waste per hour.

Continuously operating filters, such as belt filters and rotary filters,also have been found to be useful as separation apparatuses, and rotarypressure filters as are known from WO 02/100512 A1 are particularlysuitable.

Generally, solvent extraction can be used to increase the yield ofrecovered lipids 5173763 and protein from biomass waste streams.However, solvent extraction produces a solvent-extracted residue whichcontains residual solvent. Consequently, there is a need for a methodfor separating lipids and proteins from biomass waste streams providinga useful product having an acceptably low residual solvent content andcorrespondingly low toxicity effects.

There remains a need to create energy- and economically-efficientsystems to extract solutes such as lipids and proteins from post wastebiomass materials, such as animal “DAF”, flocculated and nonflocculatedanimal, vegetable and fruit wastestreams and other matter. The presentinvention addresses these and other needs.

BRIEF SUMMARY OF THE INVENTION

In one embodiment, the invention relates to a method of extracting andseparating a bio-molecule from partially or substantially dewateredbiomass. The biomass comprising proteins and desired bio-molecules, suchas lipids and/or carotenoids, may first be introduced into an agitatorvessel where it is mixed with a liquefied gas solvent. The biomass nextis passed into a rotary pressure filter (RPF) and deposited intoindividual filter cells of the RPF by rotating the RPF drum. While inthe individual filter cells and in the wash zone of the RPF, the biomassis contacted with additional liquefied gas solvent. The desiredbio-molecules (such as but not limited to lipids) are separated from thebiomass by passing the solvent through the biomass containing filtercells to obtain a solvent and bio-molecule stream through thecylindrical vessel of the RPF. In this way, bio-molecules (such aslipids) and remaining water from the biomass are extracted from thebiomass, and the protein is retained in the individual filter cells as aresult of the separation. The individual filter cells contain a cake ofaccumulated protein that is substantially moisture free and can bedischarged from the RPF. Solvent may remain in the accumulated proteinrequiring subsequent solvent removal in a further step.

In some embodiments, the biomass is pretreated in a dewatering processbefore it is introduced into either an agitator vessel or into the RPF.The pretreatment or dewatering process may comprise mixing thewastewater stream to normalize the input, contacting the biomass withone or more solvents, or by the application of thermal energy andrecovering the water and solvent. The solvent of the pretreatment maycomprise additional quantities of the same liquefied gas solvent usedwithin the rotary pressure filter.

In some embodiments, the method further comprises conveying theliquefied gas solvent, water and bio-molecules (such as lipids) to adistillation system where the constituents are separated. The distilledsolvent is re-condensed, recovered and conveyed back into the system forre-use, either in the pretreatment unit or in the rotary pressurefilter. Where the bio-molecules are lipids, the lipids may further betreated with an antioxidant to prevent spoilage, the treatmentoccurring, for example, after pretreatment and/or after distillation.The lipids may thereafter be stored in a vessel to be transported forsale. The water is separated using any suitable method known in the artand stored for disposal or re-use.

In some embodiments, the method further comprises mechanically filteringthe dry protein, and storing the filtered protein for transportation andsale. Minimal dry waste from the protein filtration process is storedfor transportation to disposal.

Another embodiment comprises a system for extracting and separating abio-molecule from biomass. The system includes a rotary pressure filterwith a plurality of individual filter cells distributed on a rotationaldrum of the rotary pressure filter adapted to receive a mixture orslurry of a biomass with at least one liquefied gas solvent, and with atleast one chamber through which liquefied gas solvent may be introducedso as to filter through the mixture or slurry held within the filtercells to extract desired bio-molecule(s) and leave a filter cakecomprising primarily protein in each filter cell. In a preferredembodiment, a heater preheats the biomass to a temperature above roomtemperature before introducing the biomass into the rotary pressurefilter. In yet another preferred embodiment, desired bio-molecules (suchas lipids) extracted from the biomass and the liquefied gas solvent arerecovered via at least one distillation column.

In some embodiments, the biomass is plant matter, such as but notlimited to, soybean, rapeseed, canola, camolina, corn, sunflower, palm,jatropha, corn germ, distillers grains, safflower, cottonseed, flax,peanut, sesame, olive and/or coconut. The biomass also can be nutsand/or seeds, or can be other fruit and/or vegetable matter. In someembodiments, the biomass is algae.

The biomass also can be the waste stream that comes from vegetableprocessing for example from carrots, kale, or tomato processing. Inother embodiments the biomass is water saturated hydrocarbonwastestreams or activated sludge that comes from industrial or municipalwastewater processing.

In some embodiments, the biomass is animal matter, such as but notlimited to 5173763 animal by-products from a meat processing plant orby-products of wastewater from a protein processing facility. Usually,the animal matter is inedible by humans but edible to domesticatedanimals (e.g., canines or felines), or farm animal feed or is waste fromthe processing of edible animal matter. In some embodiments, the animalmatter is from, for example, avian (e.g., chicken, turkey, duck, goose,ostrich, emu), porcine, bovine, ovine (e.g. lamb, sheep or goat), deer(i.e., venison), buffalo and/or fish slaughter, hatchery or meatprocessing. In some embodiments, the animal matter is beef rendering,chicken rendering, pork rendering, or fish rendering effluent. In someembodiments, the animal matter is poultry, pork, beef, veal, lamb and/ormutton. In further embodiments, the animal matter is a flocculated ornonflocculated effluent wastewater stream from an animal processingplant, such as from poultry, beef, pork, fish and dairy processing, orthe waste that arises from poultry hatchery operations, such asspent/unfertilized/broken eggs, deceased chicks or the fines that ariseout of feed processing for all animal sources. In further embodiments,the animal matter may be dairy waste, such as spilled or spoiled milk.

Suitable solvents comprise liquified gases. In some embodiments, theliquefied gas solvent is selected from butane, isobutane, propane,carbon dioxide, dimethyl ether, methane, ethane, nitrous oxide,propylene, isobutene, ethylene, sulfur hexafluoride, ammonia, gaseoushydrocarbons, gaseous halogenated hydrocarbons, fluorocarbons, sulfurdioxide, and mixtures thereof. Alternatively, co-solvents such as lowmolecular weight alcohols, blended dimethyl ether and/or ethanol may beused. Suitable co-solvents include, but are not limited to ethanol,propanol, isopropyl alcohol, 2-methyl-2-propanol and mixtures thereof.

DESCRIPTION OF THE DRAWING

Other aspects and advantages will be apparent from the followingdescription given hereinafter referring to the attached drawing.

FIG. 1 is a simplified process flow diagram of biomass separation andextraction process.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Rotary pressure filters are known in industry for separatingsuspensions, such as cellulose products, intermediate plastic products,organic chemicals, agrochemicals, instant coffee, starch,pharmaceuticals and dyes/pigments. A rotary pressure filter is acontinuously operating filter having a pressure-tight design. Itconsists essentially of a metallic filter drum that rotates at aregulated continuous speed, an associated control head, and a metallic,pressure-rated housing. The annular space between the filter drum andthe housing is sealed at the sides by means of stuffing boxes or othersealing systems. The housing is divided radially into pressure-tightchambers by means of zone separators which are held at a constant forceagainst the drum. The surface of the drum comprises individual filtercells which are connected via outlet tubes to the control head. Adetailed description of a representative rotary pressure filter may befound in WO 02/100512 A1.

When using a rotary pressure filter, a suspension to be filtered is fedcontinually under a constant admission pressure into the filtration zoneof the rotary pressure filter and into individual filter cells. A filtercake is built up in each of the filter cells of the rotating drum. Thefilter cake is then conveyed into the subsequent chambers of the rotarypressure filter for after-treatment, e.g., washing and/or treatment withsteam, an inert drying gas or heated solvent gas. The filter cake istaken off in an unpressurized zone of the filter either by means of anautomatically operating, adjustable, mechanical scraper or/and by meansof a targeted reverse pulse, typically of compressed air, nitrogen orsteam. A description of the zone separators for one example of a rotarypressure filter is provided in WO 02/100512 A1.

Heretofore, rotary pressure filters have not been used to processbiomass materials. Disclosed herein is a method of extracting andseparating a bio-molecule, such as a lipid and/or a protein, frompartially dewatered or substantially dewatered biomass that includes thestep of contacting the biomass with compressed liquefied gas solventwhile the biomass is held within individual filter cells in a rotarypressure filter. After the biomass is contacted with the compressedliquefied gas solvent, a continuous stream of extracted desiredbio-molecules (such as lipids) is entrained in a solvent stream that isdirected out of the rotary pressure filter, and a filter cake of proteinis left in each filter cell. The invention provides a robust, scalable,low-cost process for separating water and desired bio-molecules (such aslipids) from the protein(s) of a partially dewatered or substantiallydewatered biomass while maintaining desired characteristics of theprotein(s) and lipids extracted.

Applicants have found that compressed gas solvents are advantageous forextracting and separating lipids from partially dewatered orsubstantially dewatered biomass using a rotary pressure filter. In someembodiments, the liquefied gas solvent is selected from butane,isobutane, propane, carbon dioxide, dimethyl ether, methane, ethane,nitrous oxide, propylene, isobutene, ethylene, sulfur hexafluoride,ammonia, gaseous hydrocarbons, gaseous halogenated hydrocarbons,fluorocarbons, sulfur dioxide, and mixtures thereof. In someembodiments, the liquefied solvent gas is dimethyl ether, butane orpropane. Alternatively, co-solvents such as low molecular weightalcohols, blended dimethyl ether and/or ethanol may be used. Suitableco-solvents include, but are not limited to, ethanol, propanol,isopropyl alcohol, 2-methyl-2-propanol or mixtures thereof.

One preferred compressed liquefied gas solvent is liquid dimethyl ether.Dimethyl ether (also known as methyl ether) is soluble in water, andalso dissolves water. This solubility is maintained along the entirevapor-pressure curve of dimethyl ether from about −5° C. to above itscritical temperature (T_(c)) of 126.9° C.

A biomass may be collected from any suitable source. For example, if thebiomass is plant matter, agricultural waste or food processing waste maybe collected. If the biomass is animal matter, agricultural waste ormeat processing waste may be collected. The biomass as collected maycomprise up to 20 to 85% water with the remainder being suspended ordissolved solids and any impurities that may exist in the waste stream.

To achieve maximum yields of the desired products, including for examplelipids and proteins when processing a biomass, and at the same timemaximize economic efficiency of the process, it is contemplated that apartially dewatered or substantially dewatered biomass be used. For asubstantially dewatered biomass, the percentage of water is less thanabout 20% by mass or less. Preferably, the water content of the biomassentering the rotary pressure filter is less than 10% by mass, and mostpreferably less than 5% by mass.

To achieve maximum processability of the biomass and improve economicefficiency, in one embodiment, the biomass is continuously mixed in asuitably pressurized agitation vessel 4 with solvent, where the ratio ofsolvent to biomass is 5:1. A ratio of 4:1 is preferred, and a ratio of3:1 is most preferred. It is understood that the actual waterpercentages and solvent to biomass ratios employed are those that ensurethat the mixture is still flowable or movable to be introduced into arotary pressure filter for next processing steps.

A suitable pressurized agitation vessel 4 includes, for example, astirred tank 4 with a multi-blade impeller 6 that rotates at speeds fromabout 40 to about 320 revolutions per minute (see FIG. 1). The vesselinterior preferably is maintained at pressures above atmosphericpressure, such as 3 to 9 bar (gage).

FIG. 1 shows one embodiment of a simplified process flow diagram of amethod or process and system that can be used to separate and extractlipids and proteins from a biomass. Referring to FIG. 1, a pre-treatmentunit 10 for the biomass is connected to a resizing unit 8 which isconnected via a biomass supply line 64 to a pressurized agitator vessel4 with an agitator or impeller 6. The biomass is agitated to form aslurry with a liquefied gas solvent in the agitator vessel 4.

From the agitator vessel 4 the biomass slurry is introduced into arotary pressure filter 2. The agitator vessel 4 has at the tank inlet asolvent pipeline 24, and at the tank outlet, a pipeline 20 connected tothe rotary pressure filter 2. The rotary pressure filter 2 shown in FIG.1 is sub-divided into six working chambers A-F. The system in FIG. 1also includes a solvent recovery dryer 12 and a distillation column 14.

From the rotary pressure filter 2, filtrate lines 30 and 32 lead to adistillation column 14. In addition, the rotary pressure filter 2 has asolvent inflow pipeline 22, an inflow line 26 for drying gas, such asNitrogen (N2) or superheated DME vapor and an outflow line 34 for thedrying gas, and a discharge chute 36 for the filter cake. Optionally, adryer dries the filter cakes before the filter cakes are removed fromeach filter cell.

The discharge chute 36 is connected to the solvent recovery dryer 12.After removing any remaining solvent from the protein, the protein isdischarged via a discharge chute 56 to an air classifier 62 via resizingunit 60. Leaving the outlet of the air classifier 62, the protein istransferred to packaging or other desired storage or to shipping.

The filtrate containing solvent, desired bio-molecules (e.g., lipids)and water is provided via lines 30, 32 and 34 to the distillation column14, from which the solvent gas is removed via outlet line 40 providedwith a solvent condenser 42 for the solvent. The recovered liquefiedsolvent is stored in solvent storage container 16 and, via pipeline 28,connected with supply line 24 to the agitator vessel 14 and with supplyline 22 to the rotary pressure filter 2.

The distillation column 14 outlet is connected via outlet line 44 to alipid/water separation unit 18, such as a decanter, from which water isremoved via outlet line 52 to a water treatment unit 54. From the top ofthe separation unit 18, desired bio-molecules (e.g., lipids) are removedvia pipeline 46 provided with antioxidant from an antioxidant storagetank 50 via pipeline 48 to packaging or other desired storage or toshipping.

The extraction and separation sequence proceeds in one preferredembodiment as 5173763 follows with reference to FIG. 1: A biomass iscollected from a suitable source. The biomass optionally is pretreatedin pre-treatment unit 10 to remove some water. Pretreatment may includesupplying thermal energy to the biomass or supplying a co-solvent to thebiomass. If thermal energy is supplied to the biomass, the water contentmay be reduced to a level below about 20% by mass. The biomass is thensupplied to the pressurized agitator tank 4 via line 64. Liquefied gassolvent also is supplied to said tank via line 24. The agitator orimpeller 6, set at a rotational speed suitable for the biomass, stirsthe biomass to form a mixture or slurry and ensures consistency of thebiomass/solvent mixture. The mixture or slurry remains in the agitatorvessel for a time sufficient to provide intimate contact between thesolvent and the bio-molecules (e.g., lipids). It will be readilyapparent that the mixing time varies depending on the size of agitatorvessel and the flow rate of the solvent used.

The biomass/solvent mixture or slurry next is transferred from theagitator vessel 4 under constant pressure through a port 20 and intoworking chamber B of the rotary pressure filter 2, where the biomassmixture or slurry is deposited into the individual filter cellsdistributed on the rotary pressure filter's rotational drum, forming afilter cake in each filter cell. As a result of the rotary movement ofthe filter drum, the filter cells with the filter cakes are conveyedinto working chamber C. Additional liquefied gas solvent, such aspressurized dimethyl ether or other liquefied gas solvent, is suppliedto working chamber C. While a filter cake composed of protein andpossibly other non-dissolvable material is forming within each of thefilter cells, the filtrate, which consists principally of the remainingwater and extracted bio-molecules (e.g., lipids), and solvent obtainedin working chambers B and C of the rotary pressure filter by washing thebiomass with the liquefied solvent, is let out of the rotary pressurefilter through filtrate lines 30 and 32 and introduced into adistillation column 14. Following the washing and lipid extractionprocesses in chambers C and B, residual solvent content and moisture, ifnecessary, is adjusted in chamber D to reduce the load on subsequentprocessing steps. For this purpose, a drying gas at a pressure of 6 bar(gage) is supplied though inlet line 26 to drying chamber D and let outthough outflow line 34 to the distillation column 14. As a result offurther rotation of the filter drum, the filter cells with the dryfilter cakes therein are conveyed into working chamber E where thefilter cakes are forced out of the filter cells using a back pulse gasalone or in combination with a knife blade and conveyed out of therotary pressure filter. After removal from the filter cells and the drumof the rotary pressure filter, the filter cakes, consisting of proteinand any remaining solids, are taken off though the discharge chute 36and introduced into a solvent recovery dryer 12.

In filter chamber F the filter cells are washed off to remove residualproteins and filter cake residues from the filter cells. Chamber Afunctions as a vapor containment zone where any gas escaping the processis captured and either discharged or recycled.

The filtrate containing solvent, extracted bio-molecules (such aslipids) and water is provided via lines 30, 32 and 34 to inlet to thedistillation column 14. Overhead, the liquefied gas solvent is removedvia outlet line 40 and liquefied in condenser 42. The liquefied gassolvent is stored in solvent storage container 16. From solvent storagecontainer 16 the liquefied gas solvent may be recycled and returned forre-use via pipeline 28, connecting with supply line 24 to the agitatorvessel 4 and with supply line 22 to the rotary pressure filter 2. Waterand bio-molecules (such as lipids) are removed from the bottom of thecolumn 14. Lipids and water are separated in lipid/water separation unit18 or decanter. The lipids may be treated with an antioxidant to preventspoilage, and stored for further processing, or may be loaded andshipped. A palatability enhancer and/or a stabilizing agent may be addedto the proteins. Proteins also may be sifted for particle sizeclassification.

The pre-treatment facility 10 optionally may be located at the same siteas the rotary pressure filter 2 and other equipment for extraction andseparation.

EXAMPLES Example 1

Seven (7) tons of Chicken DAF from a medium scale poultry operation arecollected and pumped through the pretreatment process at a rate of 7 wettons per hour. The solids content of the incoming DAF is on average 30%solids and 70% moisture. The moisture content after pre-treatment is onaverage less than 2% moisture. To render the material according to thespecification of the pet food industry, the material is heated to atemperature of 140° C. temperature for a minimum of 20 minutes. Theresultant sludge is stored in 1 ton containers for further processing.

The sludge is processed for particle size reduction in a Macerator,obtainable from Vogelsang, to facilitate pumping into the slurry mixingtank. The processed sludge is introduced into the slurry mixing tank(e.g., Silverson Rotor/Stator Mixer) at a rate of 2 tons per hour. Theslurry tank pressure is held at 6 bar. The impeller speed is set at 8000rpm. The solvent, liquified dimethyl ether (DME), supplied byDiversified CPC International, is added at a ratio of 3:1 by mass to theincoming sludge. Mixing and particle size reduction is achieved throughthe use of a stator/rotor mixing element with an impeller speed of 8000rpm. Further particle size reduction may be achieved through the use ofan inline mixer with a speed of 8000 rpm.

The well mixed sludge/solvent solution is then metered across a controlvalve to maintain a constant mass flow to the slurry inlet zone of theRotary Pressure Filter (RPF), obtainable from BHS-Filtration Inc., ModelA6. Upon entering the RPF, the sludge/slurry mixture passes through apeek filter cloth element approximately 50 micron in opening size. Thesolids are deposited on the filter cloth, creating a cake thicknessanywhere between 7 and 30 mm.

The cake then rotates out of the slurry inlet zone and enters the washzone where the cake is introduced to pure liquefied DME solvent at aratio of 2:1 based on sludge mass. The clean solvent passes through thecake and further extracts lipids and moisture.

The slurry and wash filtrate is then stored and sent to a singledistillation column for further refinement. The solvent is evaporatedand collected at a purity greater than 99%. The remaining moisture andlipids pass through one distillation at a maximum temperature of 140° C.and are further separated by either standard decantation or acentrifuge. The resulting lipids have a moisture content of below 0.5%.The retained solvent in the lipids is below the 1 parts per milliondetectable level. Finally, the lipids are filtered in a 1 micronpolyester filter cartridge, obtainable from McMaster, to remove solidparticulate prior to packaging and shipment.

The protein stream leaves the RPF wash zone and goes to the RPF dry zonewhere nitrogen gas is passed through at a volume exchange ratio ofapproximately 10:1. This removes solvent down to 100% or less hold up.The drying gas is then passed through a compressor and condenser tocollect the solvent for reuse.

The protein stream leaves the drying zone of the RPF and discharges to0.5 bar 5173763 discharge zone where it is removed from the RPF viascraper blade, purge gas, or both. It then travels through a pressureisolating rotary valve into a solvent dryer operating at 2 bar and amaximum temperature of 350° F. A drying gas, such as nitrogen, is passedover the protein at a ratio of 2:1 solvent to drying gas. The drying gasis then sent to a compressor and the solvent is condensed to recycle thesolvent. The protein, free of solvent down to below parts per millionlevel, is discharged from the solvent dryer through a rotary valve. Fromthere, the protein is conveyed and may be passed through a particle sizeclassifier so that it may be sold according to grade and productspecification. In addition, stabilizing agents, such as PE-TOX fromKemin Industries (believed to be a mixture of butylated hydroxyanisole(BHA) and butylated hydroxytoluene (BHT)) or NATUROX from KeminIndustries (believed to be a mixture of tocopherol(s) with lecithin),are added to stabilize the lipid content in the protein. The lipidcontent in the protein stream is typically 8%.

Example 2

Seven (7) tons of carrots are obtained from a carrot processing plant.The solids content of the carrots is on average 13.5% solids, and themoisture content is 85%. Using a Comitrol® processor available fromUrschell, the carrots are resized to facilitate pumping into the slurrymixing tank. The carrot sludge is introduced into the slurry mixing tankat a rate of 3 tons per hour. The slurry tank pressure is held at 6 bar.The solvent and co-solvent, liquified dimethyl ether (DME), supplied byDiversified CPC International, and ethanol, supplied by Sigma Aldrich,are added at a total solvent ratio of 3:1 by mass to the incomingsludge. The ratio of DME to ethanol is 1:10. Mixing and particle sizereduction is achieved through the use of a stator/rotor mixing elementwith an impeller speed of 8000 rpm. Further particle size reduction maybe achieved through the use of an inline mixer at a speed of 8000 rpm.

The well mixed sludge/solvent solution is then metered across a controlvalve to maintain a constant mass flow to the slurry inlet zone of aRotary Pressure Filter from BHS-Filtration Inc., Model A6. Upon enteringthe RPF, the sludge/slurry mixture passes through a PEEK filter clothelement approximately 50 micron in opening size. The solids aredeposited on the filter cloth creating a cake thickness anywhere between7 and 30 mm. The cake then rotates out of the slurry inlet zone andenters the wash zone where the cake is introduced to pure liquefied DMEand ethanol at a total solvent ratio of 1:1 based on sludge mass. Theclean solvent passes through the cake and further extracts lipids andmoisture.

The slurry and wash filtrate is then stored and sent to a singledistillation column for further refinement. The solvent is evaporatedand collected at a purity greater than 99%. The remaining moisture andlipids pass through two distillation columns at a maximum temperature of80° C. and are further separated by either standard decantation or acentrifuge. The resulting lipids have a moisture content of below 0.5%.The retained solvent in the lipids is below 10 parts per million level.Finally, the lipids are filtered in a 1 micron filter cartridge toremove solid particulate prior to packaging and shipment.

The protein stream leaves the RPF wash zone and goes to the RPF dry zonewhere 5173763 nitrogen gas is passed through at a volume exchange ratioof approximately 10:1. This removes solvent down to 100% or less holdup. The drying gas is then passed through a compressor and condenser tocollect the solvent for reuse. The protein stream leaves the drying zoneof the RPF and discharges to 0.5 bar discharge zone where it is removedfrom the RPF via scraper blade, purge gas, or both. It then travelsthrough a pressure isolating rotary valve into a solvent dryer operatingat 2 bar and a maximum temperature of 350° F. A drying gas is passedover the protein at a ratio of 2:1 solvent to drying gas. The drying gasis then sent to a compressor and the solvent is condensed to recycle thesolvent. The protein, free of solvent down to below 10 parts per millionlevel, is discharged from the solvent dryer through a rotary valve. Fromthere, the protein is conveyed and may be passed through a particle sizeclassifier so that it may be sold according to grade. In addition,stabilizing agents, such as PE-TOX from Kemin Industries (believed to bea mixture of butylated hydroxyanisole (BHA) and butylated hydroxytoluene(BHT)) or NATUROX from Kemin Industries (believed to be a mixture oftocopherol(s) with lecithin), are added to stabilize the lipid contentin the protein. The lipid content in the protein stream is typically 8%.

Numerous characteristics and advantages have been set forth in theforegoing description, together with detail of structure and function.The novel features are pointed out in the appended claims. Thedisclosure, however, is illustrative only, and changes may be made indetail, especially in matters of size, shape, and arrangement of parts,within the principle of the invention, to the full extent indicated bythe broad general meaning of the terms in which the appended claims areexpressed. Therefore, the invention must be measured by the claims andnot by the description of the examples or the preferred embodiments.

We claim:
 1. A continuous-feed method for treating a biomass stream toseparate and recover from the biomass one or more organic products withlittle or no measurable solvent residue, comprising: introducing abiomass into a continuous system at atmospheric pressure, wherein thebiomass is continuously fed in a stream through the system withoutbatching; maintaining a water content level at or below 20% water bymass of the biomass stream by contacting the biomass with aliquefied-gas solvent, wherein the maintaining step comprises:contacting the biomass stream with the compressed liquefied-gas solvent;maintaining a pressure on the combined biomass stream and solvent duringthe contacting step, at a pressure that is sufficient to compress theliquefied-gas solvent; passing the pressurized combined biomass streamand solvents through a filter to separate the combined biomass streamand solvents into two streams: a solid, organic-extract stream, and aliquid stream; moving the solid, organic-extract stream away from thefilter and decreasing the pressure on the solids stream as the streammoves away from the maintaining step; moving the liquid stream,comprising the solvent and water, away from the filter and decreasingthe pressure on the liquid stream to evaporate and separate the solventfrom the liquid stream; and collecting the extract.
 2. The method ofclaim 1, wherein the water content level of the biomass stream ismaintained at or below 5% water by mass in the maintaining step.
 3. Themethod of claim 1, wherein the evaporated solvent is compressed andrecycled back into contact with the biomass stream at the contactingstep.
 4. The method of claim 1, wherein the organic-extract is aprotein.
 5. The method of claim 4, wherein the separated protein is anessentially non-denatured, whole protein.
 6. The method of claim 1,wherein the liquid stream of the moving liquid step includes a suspendedbiomolecule comprising a lipid or a carotenoid.
 7. The method of claim6, wherein the biomolecule is separated from the water in the moving theliquid stream step by mechanical separation.
 8. The method of claim 7,wherein the separated biomolecule is a lipid and the lipid is filteredwith a 1 micron filter to remove solid particulate from the lipid. 9.The method of claim 1, wherein the ratio of solvent to biomass at thecontacting step is between 5:1 and 2:1.
 10. The method of claim 1,wherein any residual amount of solvent retained in the separated extractis at or below 10 parts per million.
 11. The method of claim 1, whereinany residual amount of solvent retained in the separated extract is ator below 30 parts per million.
 12. The method of claim 1, wherein thedecreasing of the pressure on the solid organic-extract stream involvesa decrease to atmospheric pressure.
 13. The method of claim 1, where thepressure of the maintaining step is in a range between 2 bar and 9 bar.14. The method of claim 1, where the temperature of the liquefied-gassolvent during the maintaining step is maintained between about −5° C.and about 127° C.
 15. A continuous-feed system for the continuoustreatment of a biomass stream to separate from the biomass stream one ormore organic products with little or no measurable solvent residue,comprising: an inlet configured for introducing a biomass to the systemat atmospheric pressure, wherein the system is configured tocontinuously feed the biomass in a stream through the system withoutbatching; a chamber, connected to the inlet by piping, configured tomaintain a water level at or below 20% water by mass of the biomassstream by contacting the biomass with a liquefied-gas solvent, whereinthe chamber comprises: a solvent inlet for introducing and bringing theliquefied-gas solvent into contact with the biomass stream; a pressuregauge and regulator for maintaining a pressure on the combined biomassstream and solvent in the chamber, at a pressure that is sufficient tocompress the liquefied-gas solvent; a filter configured to separate thepressurized and combined biomass stream and solvents passing through thefilter into two streams, a solid, organic-extract stream and a liquidstream; a conveyor configured to move the solid, organic-extract streamaway from the filter and configured to decrease the pressure on thesolids stream as the stream flows away from the chamber; a conveyorconfigured to move the liquid stream, comprising the solvent and water,away from the filter and configured to decrease the pressure on theliquid stream to evaporate and separate the solvent from the liquidstream; and a collector to collect the extract.
 16. The system of claim15 further comprising a recycling loop of piping through which theevaporated solvent may be compressed and recycled back into contact withthe biomass system though the solvent inlet.
 17. The system of claim 15further comprising a separator connected to the liquid stream conveyorconfigured to mechanically separate the liquid stream into a biomoleculeand water.
 18. The system of claim 17, wherein the mechanical separatoris configured to separate a biomolecule that is a lipid and wherein theseparator is connected to a 1 micron filter configured to remove solidparticulate from the lipid.
 19. The system of claim 15, wherein thepressure gauge and regulator of the chamber are configured to maintain apressure on the biomass stream in a range between 2 bar and 9 bar. 20.The system of claim 15, wherein the chamber is configured to maintain atemperature of the biomass stream in a range between about −5° C. andabout 127° C.